/*
 * Copyright 2017 ~ 2025 the original author or authors. James Wong <jameswong1376@gmail.com>>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.wl4g.infra.common.remoting;

import java.io.IOException;
import java.io.OutputStream;

import com.google.common.util.concurrent.ListenableFuture;
import com.wl4g.infra.common.lang.Assert2;
import com.wl4g.infra.common.remoting.parse.HttpOutputMessage;
import com.wl4g.infra.common.remoting.standard.HttpHeaders;

/**
 * Abstract base for {@link AsyncClientHttpRequest} that makes sure that headers
 * and body are not written multiple times. </br>
 * Represents a client-side asynchronous HTTP request. Created via an
 * implementation of the {@link AsyncClientHttpRequestFactory}.
 *
 * <p>
 * A {@code AsyncHttpRequest} can be {@linkplain #executeAsync() executed},
 * getting a future {@link ClientHttpResponse} which can be read from.
 * 
 * @see AsyncClientHttpRequestFactory#createAsyncRequest
 */
abstract class AbstractAsyncClientHttpRequest implements HttpRequest, HttpOutputMessage {

    private final HttpHeaders headers = new HttpHeaders();
    private boolean executed = false;

    @Override
    public final HttpHeaders getHeaders() {
        return (this.executed ? HttpHeaders.readOnlyHttpHeaders(headers) : headers);
    }

    @Override
    public final OutputStream getBody() throws IOException {
        assert2NotExecuted();
        return getBodyInternal(headers);
    }

    /**
     * Execute this request asynchronously, resulting in a Future handle.
     * {@link ClientHttpResponse} that can be read.
     * 
     * @return the future response result of the execution
     * @throws java.io.IOException
     *             in case of I/O errors
     */
    public ListenableFuture<ClientHttpResponse> executeAsync() throws IOException {
        assert2NotExecuted();
        ListenableFuture<ClientHttpResponse> result = executeInternal(headers);
        this.executed = true;
        return result;
    }

    /**
     * Assert2s that this request has not been {@linkplain #executeAsync()
     * executed} yet.
     * 
     * @throws IllegalStateException
     *             if this request has been executed
     */
    protected void assert2NotExecuted() {
        Assert2.state(!executed, "ClientHttpRequest already executed");
    }

    /**
     * Abstract template method that returns the body.
     * 
     * @param headers
     *            the HTTP headers
     * @return the body output stream
     */
    protected abstract OutputStream getBodyInternal(HttpHeaders headers) throws IOException;

    /**
     * Abstract template method that writes the given headers and content to the
     * HTTP request.
     * 
     * @param headers
     *            the HTTP headers
     * @return the response object for the executed request
     */
    protected abstract ListenableFuture<ClientHttpResponse> executeInternal(HttpHeaders headers) throws IOException;

}